AN AUTOMATED METHOD FOR DELAY ESTIMATION AND TIME ALIGNMENT IN REFLECTIVE ENVIRONMENTS

In large scale sound reinforcement, separate subwoofers and full-range sources are used simultaneously to cover different frequency bands. Due to layout constraints, the subwoofers and fullrange sources are often physically separated by a few metres. This can create problems for the frequencies where both types of source significantly impact the overall response. This frequency region is called the crossover region, crossover range, or crossover band. All terms will be used interchangeably throughout this paper. The main problem in the crossover region is a lack of coherent summation of the two sources. This is due to a mismatch in the phase at a particular position. A solution to this mismatch is to apply a delay to the signal sent to one of the sources, such that, the phase is aligned, and coherent summation occurs. If the alignment is not performed correctly, the resulting magnitude will contain ripples, or even cancellation across the crossover region. Alignment is often performed by the system technician manually, which can become time-consuming, especially for larger systems. The information gleaned from measurement can be misleading, resulting in sub-optimal delay being applied. This error is usually that the sources are out time, but in phase at the crossover frequency. While this means that the two sources sum at the crossover frequency, the mismatching of the gradient of the phase means that at the outer edges of the crossover range, the quality of summation is lower than if the sources were aligned in time, not just phase.